Copolymers bearing an amide block and an ether block are very flexible materials with good impact strength, but whose transparency is relatively poor (45% to 65% light transmission at 560 nm for a thickness of 2 mm), just like their polyamide homologs without ether units.
Polyamide blocks are known to be segments that are said to be rigid with a melting point (Tm) or glass transition temperature (Tg) higher than the working temperature of the polymer, whereas polyether blocks are segments that are said to be flexible with a Tm or Tg lower than the working temperature of said polymer.
Document FR 2 273 021 describes copolymers formed from polyamide blocks and polyether blocks, the polyamide blocks and the polyether blocks being linked via an ester function. These products are sold under the trade name PEBAX® by the company ARKEMA.
Copolymers bearing polyamide blocks (abbreviated hereinbelow as PA) and polyether blocks (abbreviated hereinbelow as PE) result from the copolycondensation of polyamide blocks bearing reactive end groups with polyether blocks bearing reactive end groups. For example, it is possible to react:                polyether diol and a polyamide dicarboxylic acid,        polyether diamine and a polyamide dicarboxylic acid,        polyether diol and a polyamide diamine.        
Polyamide blocks bearing dicarboxylic chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-regulated dicarboxylic acid. Polyamide blocks bearing diamine chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-regulating diamine. Thus, the bond between the blocks is either an ester bond or an amide bond.
Polymers bearing PA blocks and PE blocks may comprise only one PA block and only one PE block.
They may also comprise several PA blocks that are identical in terms of structure of the constituent monomer(s) of the polyamide and identical PE blocks randomly distributed. Said polymers may be prepared by simultaneous reaction of the PE blocks and of the precursors of the PA blocks. A polymer is then obtained containing PE blocks and PA blocks of very variable length depending on the time at which the chain regulator intervenes during the formation of the PA block, but also on the various reagents that have reacted randomly, which are randomly (statistically) distributed along the polymer chain.
Copolymers formed from polyamide blocks and polyether blocks which have advantageous mechanical, thermal and optical properties have been sought for a certain number of years. Various approaches have been envisaged for solving this problem. In document WO 2008/006987, the specific choice of a particular monomer, such as cycloaliphatic diamines, makes it possible to obtain transparent materials.